Recently, Everett traffic engineers got the green light to replace every green light in the city. City street crews will soon swap out incandescent green light bulbs at 169 traffic signals and replace them with more energy-efficient light emitting diodes, or LEDs.LEDs are used in electronic devices such as cell phones, digital alarm clocks and even the crystal ball that descends on New York's Times Square on New Year's Eve. In addition to green lights, the city also plans to install LED lights in pedestrian signals this year.